The alternative is just using one of the discarded phones most people already have in their drawer somewhere with postmarketOS. If you're in luck it's one of the well supported chipsets
Do the phones in most people's junk drawers have unlockable bootloaders?
yes or buy one on ebay for a fraction of the price of some libre maker flavor of the month soon to be ewaste
Many second hand phones go for <100$ and are unlockable.
It's word by word the story of how I got my first such phone. I told my colleagues that I'm looking for an old Galaxy phone, and one of them had one lying around.