EDIT: Apologies. Updated with a link to what gorhill REALLY said:
Manifest v2 uBO will not be automatically replaced by Manifest v3 uBOL[ight]. uBOL is too different from uBO for it to silently replace uBO – you will have to explicitly make a choice as to which extension should replace uBO according to your own prerogatives.
Ultimately whether uBOL is an acceptable alternative to uBO is up to you, it’s not a choice that will be made for you.
Will development of uBO continue? Yes, there are other browsers which are not deprecating Manifest v2, e.g. Firefox.
I have a Chromebook, what do I need to do to get ubo? From my understanding, Firefox is not supported in the browser so I’d need to get Linux? How does security work with Linux?
https://www.mozilla.org/en-US/firefox/browsers/chromebook/
Firewalled for limiting untrustworthy connections to the computer(public networks, hotels, even work).
apparmor for protecting the kernel and controlling file access to applications. SELinux is also a good option but if you need to load kernel modules, it can take a few minutes to sign and register it. It is automated on redhat systems though.
Other than that, do your research and don’t run random scripts and install random apps.
I wonder why you’re getting downvoted
I don’t know, they’re just security measures you can take. Maybe some personal preference thing. I don’t bother with the app guard thing and SELinux is pretty annoying with my Nvidia graphics card but a firewall is something I always setup.