На Termux есть TBomb примерно 20 сообщение за минуту кое как ссылка https://github.com/TheSpeedX/TBomb
Или можешь сам поискать в github'е есть также скрипты на python'не ссылка -https://verminx.xyz/threads/python-mnogopotochnyj-bomber-exe-created-by-yagsoft.456/
I've used AutoSMS Bomber, it's a PC-based tool that can send up to 100 SMS/min. It's got a user-friendly interface and decent pricing plans. Works well with most operators, but you might wanna check compatibility before purchasing.
Yea, I think I got a solution for you. There's a browser extension called AutoPager which can send a decent amount of texts/min, free to use by the way. Check it out, it's pretty solid.