No you can't use Microsoft OneDrive to synchronise to Android app instead of Dropbox
You should use a free Dropbox account.
You can only use OneDrive, Google Drive, Box, Pdrive etc to sync between computers
Having just got a Windows Surface Go Tablet in addition to a very old
Windows laptop, I now have 4 devices including Android phone and old
Android tablet. Dropbox only allows 3 devices in total on the free version,
and I have no need of Dropbox beyond this.
Can I use OneDrive to synchronise the two Windows devices and then Dropbox
for one Windows device and both Androids?
Or do I have to use Dropbox for everything, in which case I’ll very
reluctantly have to drop the old Android tablet?
The Dropbox restrictions maybe not as bad as they first sound.
The limit of 3 devices running Dropbox applications with a free account applies to the devices that can be connected to a Dropbox product itself, via official Dropbox applications, such as the official Dropbox desktop client or mobile applications.
If your computers are using Dropbox Folder as a syncing method for Moneydance then as you have to have Dropbox Client installed, this count towards the limit. However, if you use Dropbox Connection and don’t have Dropbox Client installed, this does not count towards the limit. This limit does not apply to third party apps that connect to Dropbox via the Dropbox API. This includes the Dropbox Application Program Interface that is embedded in Moneydance mobile. Your mobile devices would only count towards the limit if you had Dropbox official app installed on your mobile devices for another reason.
You can also mix Moneydance Dropbox sync Methods on computers, say 3 computers using Dropbox Folder and any additional computers using Dropbox Connection. Another approach is to set up another Dropbox account under a different email address and set up the Moneydance folder “.moneydancesync” as a shared folder between the two accounts.