If you're installing a locally downloaded package with apt-get, you need to provide the path to the file (even if it's in your current working directory), i.e.:

sudo apt-get install ./ucsf-chimerax_1.2.5-1_amd64.deb

-- Tristan

From: ChimeraX-users <chimerax-users-bounces@cgl.ucsf.edu> on behalf of Stephen P. Molnar via ChimeraX-users <chimerax-users@cgl.ucsf.edu>
Sent: 09 October 2021 12:50
To: goddard <goddard@sonic.net>; ChimeraX Users Help <chimerax-users@cgl.ucsf.edu>
Subject: Re: [chimerax-users] ProblemI am attempting he installation of ChmimeraX Installing ChimeraX on Debian mv-10

An interesting suggestion, but

comp@AbNormal:~/Downloads/ChimeraX$ sudo apt-get install ucsf-chimerax_1.2.5-1_amd64.deb
[sudo] password for comp:
Reading package lists... Done
Building dependency tree      
Reading state information... Done
E: Unable to locate package ucsf-chimerax_1.2.5-1_amd64.deb
E: Couldn't find any package by glob 'ucsf-chimerax_1.2.5-1_amd64.deb'
E: Couldn't find any package by regex 'ucsf-chimerax_1.2.5-1_amd64.deb'
comp@AbNormal:~/Downloads/ChimeraX$

None of the missing packages are available via Synaptic.

sudo apt-get install ~/Downloads/ucsf-chimerax_1.2.5-1_amd64.deb

-- 
Stephen P. Molnar, Ph.D.
www.molecular-modeling.net
614.312.7528 (c)
Skype:  smolnar1