According to this thread you should be able to use an NBT editor to see the data on Bedrock edition. According to this github page an NBT editor is usable as long as you have the mono, and mono windows, framework which is possible to get on Ubuntu.
There are two issues that I foresee, 1 is that you are using a Linux server that you don't have total access to, a potential solution to this would be to transfer your world save to another device, and use a NBT editor locally, and then re-upload it. The 2nd potential issue is that you are not able to copy the NBT data between characters, a solution to this would be to copy down the data somewhere and manually give the items and such to your character using game commands.