Android is Losing a Big Feature

There will not (edit: as in something that can genuinely be called F/OSS), because the demarcation of government property (e.g. FCC) and your property must exist in-silicon. Attempts to thread that needle results in poor battery life due to separate modules (e.g. PinePhone, Ringo), or is an outright grift that destroys honest attempts (Purism's phone).

But (cellular-free) Wifi handhelds have a niche-case here to flourish in such goals, especially as wifi/LoRa/etc reaches critical mass in areas that used to rely on cellular.

There is already a GNU/Linux phone that's viable for hackers/developers: PinePhone Pro.
It works, but there are many compromises. It needs more hackers/developers/users to keep making it better and build critical mass.
https://pine64.org/devices/pinephone_pro/

It's called ubuntu touch - still being actively developed by the community.

Not entirely open, but SailfishOS is a Linux smartphone polished enough to be your daily driver.

Nice thought but it will never happen. Part of the purpose of the S.M.A.R.T. Phone is tracking you.

We don't wanna opt out of a modern society just cuz someone establishes another monopoly

There are cases where it's not that simple. You know Play Store is filled with illegitimately geo-blocked apps? And there are fascist and communist countries where Play Store is totally blocked.

Not an option. You're saying, don't install an app you need to access your banking and money. Or literally anything from food ordering to delivery apps you need on some courier jobs.
unless idiot normie users listen to us and break the Google monopoly, we have no choice . just as many of us forsaw. Forced surveillance on everything. Windows Recall, Apple Client scanning and more

Maybe it's possible for modded apps like Revanced project, but I will keep my expectation low because those app protection integrity are hardcoded into the source code

Well the GrapheneOS crowd are pretty annoyed about it: https://grapheneos.social/@GrapheneOS/112878070618462132

F-Droid, Obtainium, and NeoStore are your new friends. Hurry up to meet them, they provide what you need.