I also have this problem, "Object reference is Nil." when I start the Lazarus !
XUbuntu 20.04 LTS 64bit fresh installation on new laptop (Acer Intel N5000 CPU, 8Gb RAM, 128Gb SSD),
FpcUpDeluxe FPC Fixes (v3.2.1), Lazatus Fixes (v2.0.13), date 2021.05.15.
Installed all dependencies for Lazarus, maybe something else is missing for the IBX ?
p.s. Firebird 3.0.7 64bit installed before Lazarus and IBX !