SDM 845 devices, Especially OP6/6T and Xiaomi Poco F1 has changed the landscape for PostmarketOS(Still is not for everyone though).
Firefox/Fennec F-Droid is indeed great (Especially since UBO is supported), But unfortunately in Android almost every enthusiast project involves privilege escalation and in this case F-Droid auto update apps requires one too.
Just to note, There's a full-desktop Firefox available with mobile layout in PostmarketOS for Linux Phones. Here's the device I drive daily[1].
[1] https://wiki.postmarketos.org/wiki/Xiaomi_Poco_F1_(xiaomi-be...