I need access to my obsidian notes on the go as well as at home on my desktop; I would use them more on the go.
I use OneDrive - which is expensive for me and I use it because I have to use it.
My personal expenses are a private matter and believe me when I say that I cannot afford to pay for Obsidian Sync.
This was previously mentioned (although not descriptively enough) at this hyperlink: Enable mobile app to use OneDrive - #2 by WhiteNoise
Proposed solution
Add OneDrive synchronisation to Obsidian Mobile. There’s no point in not doing it (even for your marketing purposes) because you allow mobile synchronisation with iCloud Drive.
Current workaround (optional)
Transfer notes through Joplin (with OneDrive as a synchronisation target) on Joplin Mobile and Joplin Desktop. This way you can transfer notes to and from Obsidian through your desktop/laptop.