I have a method that works on android
1.- install Total Commander, give it all the permissions
2.- browse the __data_org folder.telegram.messenger/files/Telegram/XYZ
3.- where the XYZ will be the folders Videos, Images, Documents, etc etc at this moment these folders should have hundreds or at least dozens of files (check that those folders contain files), I recommend saving those folders in favorites in TOTAL COMMANDER
4.- Enter the telegram settings and delete all the cache, once done enter the private channel from where you want to download files.
5.- download the files you want to download, depending on what it contains will be in its respective folder.
6.- Enter the respective folder (the favorites you saved) and select the files you want to save. Click on the button (2 papers) copy/move, click on >> to select the folder where you will move the selected files and finally click on MOVE OR COPY
7.- and Voila, the selected files of the private channel will be where you saved it.
Greetings
