I already bought many of the soured books and really do not want to buy them digitally too… is there a way to unlock the digital ones with some way of showing proof of purchase?
There is no way. If you want both the digital and physical products, you have to buy both separately. Alternatively, you can them both as part of physical-digital bundle (which may or may not save you money after factoring in shipping fees), but only from Wizards' website.
Also note that, depending on how you want to use things here, you might not need to buy whole “books here. A la carte purchases might work better for you. The buyers guide in my signature may be of help in that regard.
I already bought many of the soured books and really do not want to buy them digitally too… is there a way to unlock the digital ones with some way of showing proof of purchase?
There is no way. If you want both the digital and physical products, you have to buy both separately. Alternatively, you can them both as part of physical-digital bundle (which may or may not save you money after factoring in shipping fees), but only from Wizards' website.
If you want more information on about it, here is a thread about it:
Hardcover Books, D&D Beyond and You FAQ
Check Licenses and Resync Entitlements: < https://www.dndbeyond.com/account/licenses >
Running the Game by Matt Colville; Introduction: < https://www.youtube.com/watch?v=e-YZvLUXcR8 >
D&D with High School Students by Bill Allen; Season 1 Episode 1: < https://www.youtube.com/watch?v=52NJTUDokyk&t >
Also note that, depending on how you want to use things here, you might not need to buy whole “books here. A la carte purchases might work better for you. The buyers guide in my signature may be of help in that regard.
Trying to Decide if DDB is for you? A few helpful threads: A Buyer's Guide to DDB; What I/We Bought and Why; How some DMs use DDB; A Newer Thread on Using DDB to Play
Helpful threads on other topics: Homebrew FAQ by IamSposta; Accessing Content by ConalTheGreat;
Check your entitlements here. | Support Ticket LInk
You can also use the homebrew tools to replicate many of the functions in the character sheet.
Birgit | Shifter | Sorcerer | Dragonlords
Shayone | Hobgoblin | Sorcerer | Netherdeep