"Was a long time ago" in Telegram, what does that mean?

Either block or hide the visit time.

Probably blocked you. Someone blocked me once, and immediately their photo disappeared and their status—it was a long time ago.

If he logs in often, then if he had removed the visit, it would say - was recently

The person has blocked you. If you try calling, you'll hear short beeps, and if you text, one checkmark will always appear.

Most likely, this person has blocked you. In Telegram, there are two display modes for a user's last seen time: the exact time and the status "recently" (if they have disabled time features in their settings). If you don't see either of these and only see the status "a long time ago," then you can assume the person has blocked you. In principle, this same status could apply to a deleted account or a profile that hasn't been used in a long time. But you claim the person uses the messenger, so it's just a block.

Statuses follow a specific algorithm. If it says "last seen recently," it means from 1 second to 2-3 days. If "last seen within a week," it's from 2-3 to 7 days. If last seen within a month, it's from 7 days to a month. However, if it says "last seen a long time ago," it means more than 30 days. But if you're sure they use Telegram regularly, it could also mean you've been blocked.

You are blocked.

And for me, one person who passed away has the date of their last visit displayed.

This means you have been blocked.

So, you're blocked by him.

Компании, операторы сотовой связи, через некоторое время, насколько я знаю через 3 месяца не использования, могут перепродать сим карту. И вполне возможно новый клиент зарегестрируется, например, в телеграмме: ведь теперь коды для восстановления и входя он может получить, даже для аккаунта, которые не он регистрировал

it means you were blocked
or user dont use telegram for 30 days

добрый вечер,если аватарка пропала и осталась только буква-вас заблокировали(но переписка,по моему,должна остаться)
статус "был(а) очень давно" означает,что вы у пользователя в черном списке с очищенной перепиской