In Sweden it hasn't been possible to buy paper passes at stations for several years. As a matter of fact there are no physical ticket offices from SJ at all available any more, not even in Stockholm. 

Yeah that I know, but SBB has still a lot of ticket offices. Deutsche Bahn and ÖBB as well and until now they (all?) sold Interrail tickets as paper version. 

As long as the app is providing so many wrong information (not valid trains, not valid pass, blabla), I don’t think it is a good idea to push people to even more digital passes (even if the so or so count already for 95% of the sales).

I plan to travel to Sweden with a paper pass in February. Are paper passes accepted in Sweden? I don't like and don´t want the app, it's the only app, that requires you to lock your smartphone screen, it's annoying. I prefer a paper pass.

Yeah, paper passes are accepted in Sweden. 
Just EURAIL Group wants to get rid of them it seems in the near future. Not caring about people without a smartphone and older people who are not so used to using a mobile app.

It is no problem to travel with a paper pass in Sweden. I did it this summer. 

Thanks. Can you tell me where to buy bus tickets in Swedish cities? From Gällivare station to Dundret and from Kiruna to Jukkasjärvi. Are there special places to buy in advance or is it bought from the driver on the bus or from a machine on the bus?

These are NOT citybuses, but regional lines.

You can buy from and pay driver=-but NOT in cash-only by card-that is the highest price. That works about anywhere in SE-still. It is possible as such that only full fare and no discount tix are sold then (unsure). Check norrlandstrafiken.se.

For locals the most common method is usually by an app on their fone.

Was myself in SE last sept-paper pass for 3 months-and could easily get by all the time without any cash (had a little left from last visit-but the coins were out of use), paid all the time by card.

Back to subject: f.e. now in BE paper passes are only sold at 1 outlet-mobile directly via all outlets that do INTERnat. tix. The Swiss can also order via this site or-when they hold the usual GA-just make it an outing and visit DE at some convenient point. Germans start to scream out loud when such things start to vanish-also all the time if one cannot pay with cash, even very large amounts.

SNCF does since this yr not give out any paper printed tickets in their machines-you have to give full details, also name+fone nr+@mail and then get them sent to your @mail.

I have no problem paying with cards. Are visa debit cards accepted on buses and shops in Sweden? Or does it have to be a credit card?

I can't find any information about where to buy the bus ticket from Gällivare to Dundret but I guess that you will be fine buying it from the driver. If not you would need to download the app for the public transportation of Gällivare and buy the ticket there. Here you can find a pdf with the timetable for the bus in Gällivare.

http://www.gellivare.se/kommun/hitta-direkt1/turlista/

Here you can find all information you need about the bus between Kiruna and Jukkasjärvi.

https://ltnbd.se/en/fares-and-tickets/