@Switch BlaydeMost of my stories are military, and have quite a few characters.
I have my own reference lists, and a much abbreviated list for readers.
Typically, I provide Name, Rank, (nickname if frequently used) ethnicity, and initial Duty in the TO&E, sometimes primarily weapon. Perhaps some tidbits commonly known to the personnel in the unit.
Often in the character list I include small details that would be obvious if You were there, such as James is the tall Black guy from Detroit, and Harris is the buck-tooth kid from Tennessee.
Or, Smith is the highest ranking guy, but he's a Medic, or a Sniper, so he won't be taking over the Platoon when the Lieutenant becomes a casualty.
In my World War Two story the Character List is pretty much the information that the Platoon Leader and Platoon Sergeant have to assign the men to various positions in the unit. It is also something all the members of the Platoon would know about each other before their first combat.
As casualties mount, Replacements are strangers, who Often become casualties and are gone before anyone knows them. This was common in the US Army after June 6th 1944. I show this, not tell it.
At the end of the story I have a list of all of the characters, mentioning if they lived, and a short blurb, or if they were wounded, or died.
I also included a list of Historical characters. Mostly the historical characters only do what they are documented to have done. Usually, something the characters witness.
I intend the character list to be available for those who Want it. Otherwise, it is easy to skip to the 1st chapter at the top of the page.
Some people have it as a separate tab. If you don't have multiple screens, such as a phone, on the top of each page is the Story Title. Click it brings you to the Table of Contents. You can look at the List, then use your back button, or the chapter list to get back to where you were reading.
I prefer to print Character Lists, so I can add notes the author may not have included.