The things you'd normally use Nextcloud for is not the sort of thing that I would ever trust to be hosted for free, there's bound to be a catch (whether that is the service just disappearing over night, your data being collected and used for some nefarious purpose, etc).
It's definitely worth either self hosting, or if you're not able to, paying for some VPS to host it on.
That all being said, if you really want to go the route of free hosting, Nextcloud apparently do list some providers on their website.
I'm all for Linux, and would normally be the first person to cheer you on for switching to Linux... if this were your personal computer. For a work device though? All bets are off, and you really shouldn't do that sort of thing without express authorization from whomever manages IT & security policies at your workplace - otherwise you risk losing your job, and potentially even worse things if the data that you're being trusted with gets compromised because of the modifications you made.
If for something regarding work, your end thoughts are:
Then it may be a good idea to re-think what exactly the pros and cons are of what you're doing, because the cons are generally going to outweigh the pros.
This sort of thing also gives Linux a bad reputation at your workplace, when you inevitably get caught. When someone tries to propose going through the proper channels and inquiring about IT actually supporting the usage of Linux at your workplace, all of IT and management are only just going to think back to "that one person who really went against the grain and tried to use that Linux thing". Same concept goes for when you try to push someone into Linux who doesn't have a good use case for making the switch over to Linux (or see the "Linux evangelists / fan people" phenomenon that in of itself is present all over Lemmy).