Cannot install boards

I am running Linux Feodora 31 and Arduino 1.8.12. I followed the guidance on adding boards but new boards do not show up. I want to program the Adafruit Trinket. Added the appropriate url under preferences, opended Board under Tools, but the Trinket doesn't show up. What is the issue.
Thanks.

ov10fac:
Added the appropriate url under preferences, opended Board under Tools, but the Trinket doesn't show up. What is the issue.

You missed a step. You need to install the correct boards platform for your Trinket via Tools > Board > Boards Manager, as shown in this tutorial:

If you have the classic Trinket, then install Adafruit AVR Boards. If you have the Trinket M0, then install Adafruit SAMD Boards.

After doing that, you will then see the Trinket board listed under the Arduino IDE's Tools > Board menu.

pert:
You missed a step. You need to install the correct boards platform for your Trinket via Tools > Board > Boards Manager, as shown in this tutorial:
Installing Boards | Adding Third Party Boards to the Arduino v1.6.4+ IDE | Adafruit Learning System

If you have the classic Trinket, then install Adafruit AVR Boards. If you have the Trinket M0, then install Adafruit SAMD Boards.

After doing that, you will then see the Trinket board listed under the Arduino IDE's Tools > Board menu.

Interesting, I did try to use the "Board Manager" at the top of the Boards drop down, but when I clicked on it all that happened was that I returned to the ide. I have always started the IDE by using the "Activities" feature of Fedora.
So I decided to check for errors and started the IDE from the command line. Strangely when I clicked "Board Manager" this time the board manager opened up and I was able to add the adafruit boards. Strange behavior indeed, but the problem is solved, and if anyone else running Fedora 31 has this issue, maybe it will work for them.