I'm a month or so into switching from Windows 10 to Ubuntu. I've never lasted this long in prior attempts to switch over.
Gaming has been quite good. Steam just works for 99% of the games I've tried, with the 1% being one or two minor bugs in games that otherwise worked fine. Lutris, on the other hand, did not work at all. 0% success rate installing or running games.
Linux does still seem brittle and/or unnecessarily complicated, though. For example, I have a super common nvidia card, and my first post-install experience was having to boot into safe mode to fix the drivers. Then Ubuntu updated the drivers and my screens didn't come back up. I had to hard-reset to get them back. And I have yet to get NUT installed and configured correctly so I can have the PC power down gracefully when the UPS runs low, something which is trivial in Windows.
Is all the frustration worth it to have an OS that isn't selling me ads and trying to move me to a cloud account? Probably.
Heat pump water heaters already exist, but I think they're pretty expensive compared to gas/resistive heat.
I wouldn't be surprised if electric tankless water heaters are indeed infeasible under this mandate. Heat pumps generally aren't powerful, and tankless heaters require enormous amounts of power while in use.