GP was talking about "having thrown away a workable peace deal", which in this context almost always refers to the purported peace deal that fell apart in 2022. In any case, the only other peace deal that is currently officially on the table as far as Russia is concerned is basically the same.
What's actually workable in the end depends solely on how far the West is willing to go, IMO. There's no realistic scenario in which Ukraine retakes all the captured territories without direct Western military involvement - air at the minimum - which is certainly not politically tenable in either US or Europe (although my personal opinion is that both will eventually regret not getting directly involved now, because they will be forced into a larger war later anyway).
Russia will definitely not give up Crimea without getting military defeated there; quite aside from any military value of Sevastopol, the symbolical and political value is just too high, especially for a regime that desperately needs to be seen as "patriotic" by the populace - that is their only real source of legitimacy in the absence of real democracy. Abandoning LNR and DNR would be easier in some ways, but harder in others because the government agitprop has already spent so much time vividly describing how "Ukrainian Nazis" are supposedly ethnically cleansing Russian speakers to justify the invasion, abandoning them now would also be very costly in terms of popular support.
OTOH I could see the pre-2022 de facto borders as something Putin would accept. They could still justify the war then by claiming that, at least, LNR and DNR were "rescued" and are now safe from further depredations, and that people from other regions that couldn't be "liberated" will be resettled, so - mission complete, oooorah etc.
However, I don't see why they would do that if the West keeps dragging its legs on military support to such an extent that Ukrainians can't even reliably hold what they already have. The way things are going, Russia can keep doing what it's doing, even despite the insane cost in human lives, for longer than Ukrainian military can hold the line. Ukrainians have less of basically everything - artillery, drones, people. They make do by making much more efficient use of what they have than Russians do, but it's still too skewed to be sustainable.
And meanwhile the West hasn't even drawn any clear red lines on how much of Ukraine Russia would need to take before the support would be seriously ramped up - if at all. So then, when Russia sees that support is already at levels insufficient to sustain Ukraine, and it's likely to dwindle significantly with Trump, and it has the upper hand in terms of momentum right now... I don't see why they'd suddenly want a deal.
OTOH if US and Europe doesn't get involved directly but start treat their role as the "arsenal of democracy" in this conflict seriously, it might just be enough for Ukraine to hold the line in the east and in Kursk. And then they might be able to trade that captured Russian land for a peace deal with some concessions - maybe not quite pre-war borders, but at least push the new border away from large cities like Kharkiv and Kherson. However, any such deal would be pointless for Ukraine unless they get proper security guarantees; and, given the whole history with Budapest Memorandum, the only guarantee that Ukraine will actually believe in at this point is NATO membership. AFAIK that is the main reason why popular support there is still in favor of continuing the war and rejecting the current Russian offer - they elected Zelensky largely as a peace offering to Russia and effectively acknowledged the de facto existence of LNR and DNR, and all they got for that is an even larger invasion, so it's a "fool me twice" kind of deal now.
Appreciate the detailed response, and it seems we are very broadly on the same page.
Assuming no further military push from the West -- do you think the Russian side would acquiesce to some form of "Cease fire along current lines, but no legal recognition of the territorial claims, and no lifting of sanctions or arrest warrants, and no return of seized foreign assets"?
(That's very far from my own ideal outcome, but I'm just trying to get sense of how you see the situation).
It's hard to say. It would be essentially the same thing they already did back in 2015, so there's precedent. But back then it happened IMO because they didn't think they were sufficiently prepared in economic and military terms to openly wage war, so Russia took as much as it could with the "northern wind" (the euphemism separatist forces used to refer to direct Russian involvement in combat) and then took a break to prepare for the real deal.
So I think now they would do it if they believe that taking another break would benefit them more than it benefits Ukraine. But, again, looking at post-2015 developments, it's not clear to me why they'd think that. The reason why their advance in the east was so much slower than elsewhere is that Ukraine had a massive effort to build fortifications and infrastructure around them under Poroshenko. It's why Ukraine could hold Avdiivka for so long despite it being less than 10 miles away from Donetsk, and it's partly why Russian losses are so high. Russia has managed to punch through that line in several places in this past year despite those high costs, but if they stop the advance now, that kinda defeats the purpose of that. And meanwhile if Ukraine could get some respite, they would surely spend a lot more resources on another defensive line along the new border, probably with significant Western assistance this time, as well (since "defensive" military aid generally enjoys higher popular support, countries like Germany might be more willing to do that even if they aren't willing to send more tanks and missiles). As well as building new munition factories etc, likely also with Western defense companies involved. It would also mean the return of millions of Ukrainian refugees, reinvigorating their economy.
This all assumes that Russia wants to take as much Ukrainian territory as they can get away with, in the long term. But, given that the war literally started with them trying to capture Kyiv, I think it is a safe assumption. If they gave up on that goal since then, they wouldn't be pushing so hard now despite the losses.