Dilemma with open RNote files

[TimberclawDev]

Hey,
i just installed RNote on my Surface running Ubuntu and am automatically syncing the files to my nextcloud instance.
Am gonna use RNote for school and wanted to use it to have access to my files on all my devices, even when im traveling w/o my laptop and needed to learn.
Sadly, i didnt see that RNote uses an own file format, which makes absolute sense, just didnt think of that.
But that means, that i cant access the files on my phone and would have to install the RNote app + nextcloud on the devices i would want to use them.
I cant install RNote on my families laptop due to it being work laptops, so even if they would carry their laptops with them, it just wouldnt work.
Any ideas for a way around that???
Thank you for your answers in advance c:
Sorry, if my english is not the best, its not my primary language :)