Previously, I tried Massplanner and Jarvee. Massplanner was excellent, but both are a bit expensive. Currently, I have only 2-3 accounts to automate, so I am using Gramaddict. I installed it on a Raspberry Pi and used some of my old phones in conjunction with it. It is working perfectly, operating 24/7 without additional costs (except for internet and electricity charges).
In my opinion, if you have a small number of accounts, you can try Gramaddict. It is open-source and can be used with a PC, Raspberry Pi, etc