For phones you can find ratings based on ease and cost of repairability (assuming you do everything yourself). Is there such a source for choosing a motorbike or car that you want to maintain yourself completely?
None that I am aware of.
There are articles on motorcycle websites that have various lists such as 'Top 10 Low Maintenance Bikes' and such. As well, there are various attributes of certain vehicles that are low maintenance. For example, a motorcycle with a shaft drive does not require chain and sprocket adjustment, lubrication and replacement thus a reduced maintenance schedule. Be aware that reduced maintenance cost typically increases manufacturing cost and that is passed onto the consumer and built into the overall price of the vehicle. Typically this capital expense will not total the cost of maintenance for the life of the vehicle but it can price a vehicle out procurement range. Another attribute of a low maintenance motorcycle is the cable clutch, cables require replacement. A hydraulic clutch requires brake fluid to flushed occasionally, which is a relatively low cost.
A Consumer Reports subscription on their website will yield you ratings related to motorcycles and reliability but since I do not have a subscription that is all I can share.
I feel comfortable recommending Consumer Reports as it a not for profit entity that is NOT hawking goods other than a subscription of course.
I hope this answer is useful to you, best of luck.