FFUpdater supports Android 5+: https://f-droid.org/packages/de.marmaro.krt.ffupdater/ You can install a lot of browsers from there, maybe one of them supports this phone: https://github.com/Tobi823/ffupdater
Also check slimsocial, it's a facebook client, supports Android 4.4+ and it lists arm7 support: https://f-droid.org/hu/packages/it.rignanese.leo.slimfacebook/
And new Chinese phones (Redmi, HMD, etc) are really cheap, they are good as a backup smartphone. I know it sounds terrible, but you can't really do anything with planned obsolescence. Our time is short on this planet, waiting for websites on old hardware simply doesn't worth it, you should spend this time on more important things.
I use wallabag. There is paid hosted version, but you can install it on your server. You can tag, star and mark read/unread your bookmarks. There is a webapp, browser extensions, mobile apps for all platforms, and apps for ebook readers.