I generally avoid booking hotels that advertise rates in a foreign (to them) currency, unless it is known that they actually do charge you in that foreign currency, or their private exchange rate has been reported to be fair. One way to avoid the scam is to use points.

The DT Minsk has been scamming guests for years, and probably very few people complain so I assume they feel they can continue this. The overcharging / underadvertising is quite significant as the OP has reported. Perhaps a list of good and bad hotels should be created so that prospective guests can inform themselves about the hotels that engage in this scam.

Good: the DT Zagreb advertises in euros but surprisingly their private exchange rate was in my favour. The HRK is semi-pegged to the euro so it still fluctuates a bit. But even using the most unfavourable exchange rate between the time of booking and stay, the amount of HRK I was charged was at least 0.5% lower than the euro rate quoted.

Hilton Sofia advertises in euros and accepts euros in cash at the fixed exchange rate between EUR and BGN. The main card networks appear to all use the fixed exchange rate so it doesn't matter whether they charge cards in EUR or BGN.

I asked on the FT thread about the HGI Tirana and it was reported that a reasonable EUR/ALL rate was used.

Unknown:
Hilton Budapest displayed a board at the front desk with their private exchange rate of the day. However I used points to avoid any chance of being scammed, and I checked in and out at the lounge so I didn't manage to read the rate at the front desk.



Hilton Prague advertises in CZK, but the front desk seems to do a roaring trade in euro/CZK cash exchange at much poorer rates than available in the city.