Hello,
I have been adding members in Telegram since last 2 years.
I can give you the software I have developed.
You need to have a windows VPS server and a NordVPN subscribtion.
In one group you can add 1000 members in 24 hours( you can add more but there is a chance that Telegram will impose restrictions on the group which will inhibit you from adding more members in group).
For multiple groups you can add 1000 in each group.
You will have to get multiple Telegram accounts from a website I say.... And there is a procedure to be followed to create this Telegram accounts.... If you want you can buy and create from website or I can sell you the Telegram accounts afterwards.... I will give you 2 Telegram accounts for trial...
Contact me and I will give you two days trial of the software.
Regards,
Pravin Solanki.