You’ll find those from the app Mobile Settings (not in the Settings app).
And setting up Flathub (sorry, forgot): PureOS Flathub Setup | Flathub (flatpak remote-add --if-not-exists flathub https://dl.flathub.org/repo/flathub.flatpakrepo)
And btw.: flathub seems to have a new mobile apps category (may not mean that they work with L5 but probably fit screen better). See: https://flathub.org/apps/collection/mobile/