Hi,
This works fine in nominatim: "дружба-2, бл.515"
As you know the issue is the entrance id.
ref is used for road numbers. I guess in some countries nominatim does index those too.
I've lived in Druzhba-2 since '89, so I can add entrance letters for the whole neighbourhood. However, I don't see the benefit. It won't change anything. if search is not working and applications don't display it, what's the point?

I was wrong. Russians use only ref=* indeed.
node/1142515549
Maybe we should follow Moscow as example and eventually renderers and geocoding/reverse geocoding engines will be changed to respect entrances.

I have started these tests because https://nominatim.openstreetmap.org/ barely works in Sofia for жк addresses.
Should we tag the whole city and then ask the developers to adapt nominatim and the renderers for Sofia? : )

Yes, I agree with your logic.
But how are you going to approach the problem that not a single geocoding engine works this way? And how do you understand the text in the wiki: "inner" number of staircase / "outer" address of staircase?

Hi,
I've spent a little more time on this with Overpass Turbo. Russians are tagging entrances with addr:housenumber + ref
I have asked the support of MAPS.ME (in Moscow) about their search and here is the response:
MAPS.ME Support (MAPS.ME)
Nov 18, 12:45 MSK
Hello!
The app doesn't support search by building entrances yet. So far, we don't plan to add it. However, the more similar requests we get from users, the more likely that we'll consider the option.

The wiki (entrance=*#Entrances_and_addresses) describes the ref tag should be used for INNER number of staircases. For OUTER number we should use addr:housenumber.
So I guess we should decide if we should tag entrances with
(addr:housenumber="бл.555 Б")
or (ref="Б" and addr:housenumber="бл.555")
or (ref="Б" and addr:housenumber="бл.555 Б")

I think this is part of this discussion https://forum.openstreetmap.org/viewtopic.php?id=30295
or
https://forum.openstreetmap.org/viewtopic.php?id=22015
The wiki says in several articles "use addr:housenumber for entrance=*". This works in Russia. It is searchable. I've noticed Germans use address places in Berlin. addr:name is another option, but the wiki says that this is reserved "named places". I think we should think about osm.wiki/Good_practice#Don.27t_map_for_the_renderer
P.S. Do you speak Bulgarian?

Hello,
My main concern is the search capabilities of Nominatim and android navigators such as ME.MAPS and OSMAND. According to entrance=*#Entrances_and_addresses we must use ref. Also Nominatim is importing ref and ref_int according to osm.wiki/Nominatim/Development_overview
However, "search" is unusable in its current state. I've found that the only usable format in Nominatim is addr:housenumber in cyrillic бл.999-Д for entrances and avoid addr:street completely for buildings in suburbs.
But the searchable field for MAPS.ME is addr:name.
Lets discuss the subject in details somewhere else.
Thank you for your interest :)