HEX 1B3F67

[96jtaylor]

Seems to be Russian.  Callsign appeared as RF 81767.

[Joolde]

Based on what I can find, it might be a Russian Air Force Sukhoi Su-30 or Su-35..

RF-81760 is an Su-30SM
RF-81761 and 81763-81766 are Su-35
RF-81768 and 9 are Su-30SM

But I couldn't find any information online about RF-81767.

EDIT: probably related to this: https://ac.nato.int/archive/2021/20210420_Baltic_Intercepts