You won't get support of Samsung Pay, Samsung Pass, Good lock and it's module like Edge lighting, Sound Assistant, Task Changer, etc and Secure Folder will be provided in next update i guess. Plus A51 has CA and is supported for 3 years. I bought M51 yesterday for its SD processor and battery but didn't knew on software side it's complete shame compared to A51 on same Price.
i also feel same i always say all to buy a series rather than m because people look for a series features nd think both series have same software but reality is really hard to accept m series is just normal phone like other brand with normal features no special Samsung features for which we buy
U should have researched a bit noone recommend for m series its for user who want best performance and battery other than that nothing matters them or for users like our parents who want to use a good lag free device but don't use much features