All Termux repositories previously hosted on JFrog Bintray are down since 1st May, 2021. This means that all repositories hosted on dl.bintray.com domain are not available anymore. There nothing can be done on our side because Bintray service announced its sunset.

Ign:2 https://dl.bintray.com/grimler/game-packages-24 games InRelease
Ign:3 https://dl.bintray.com/grimler/science-packages-24 science InRelease
Err:4 https://dl.bintray.com/grimler/game-packages-24 games Release
  403  Forbidden
Err:5 https://dl.bintray.com/grimler/science-packages-24 science Release
  403  Forbidden
Get:1 https://grimler.se/termux-packages-24 stable InRelease [13.1 kB]
Get:6 https://grimler.se/termux-packages-24 stable/main all Packages [21.6 kB]
Get:7 https://grimler.se/termux-packages-24 stable/main aarch64 Packages [269 kB]
Reading package lists... Done
E: The repository 'https://dl.bintray.com/grimler/game-packages-24 games Release' does not have a Release file.
N: Metadata integrity can't be verified, repository is disabled now.
N: Possible cause: repository is under maintenance or down (wrong sources.list URL?).
E: The repository 'https://dl.bintray.com/grimler/science-packages-24 science Release' does not have a Release file.
N: Metadata integrity can't be verified, repository is disabled now.
N: Possible cause: repository is under maintenance or down (wrong sources.list URL?).

What you should do as Termux user (only for Android 7+)

You need to pick a one of the available mirrors by using utility termux-change-repo or manually edit sources.list by replacing the Bintray URL with value obtained from Termux Mirrors List.

Beware of third-party scripts claiming theirselves as repository fixers! They could install untrusted GPG key and redirect your Termux installation onto malicious repository. Official tool for changing repositories is bundled within Termux and called termux-change-repo.

Usage of termux-change-repo is simple:

1. Select one or more repositories for which you want to change mirror by tapping "space" and navigating over list by up/down arrow keys. Tap enter to confirm the choice.
   
2. Pick a mirror, it is recommended to begin with mirror hosted by Grimler. Same as previously, navigate over list by arrow keys, pick mirror by space key and confirm choice by pressing "enter".
   

Highly recommended to run pkg upgrade after changing mirror.

If you get E: Repository .. changed its .. value from .. to ..

Package manager can show you a notification with prompt which look like this one:

E: Repository 'https://grimler.se/termux-root-packages-24 root InRelease' changed its 'Origin' value from 'Bintray' to 'termux-root-packages-24 root'
E: Repository 'https://grimler.se/termux-root-packages-24 root InRelease' changed its 'Label' value from 'Bintray' to 'termux-root-packages-24 root'
N: This must be accepted explicitly before updates for this repository can be applied. See apt-secure(8) manpage for details.
Do you want to accept these changes and continue updating from this repository? [y/N] 

It is completely normal. Answer "yes" to this prompt. It will be shown only once per repository, so package manager will ask you to confirm for game-repo, science-repo, etc separately but you will need to confirm them only one time.

Do not use Termux app from Google Play. It is deprecated.

Use Termux application from F-Droid, here is the link: https://f-droid.org/en/packages/com.termux/. Google Play variant is deprecated, doesn't receive updates and contains issues as well as outdated repository URLs.

Before migrating to F-Droid Termux version, uninstall the application and all add-ons like Termux:API, Termux:Styling, Termux:Widget and others. This is a required step because of signature mismatch between F-Droid and Google Play variants. If you need to back up data before uninstalling app, you can use suggestions from https://wiki.termux.com/wiki/Backing_up_Termux.

Remember that Android 5.x - 6.x is NOT SUPPORTED!

Android OS version range 5.x - 6.x has been deprecated since 01.01.2020 and no longer worked on anymore. Provided here repository workarounds are only for Android 7.0. We never announced that bringing back support of legacy Android versions.

If you managed to put an URL of our mirrors to your sources.list and upgrade your legacy Termux, do not complain about broken installation. If maintainers marked something as unsupported, perhaps there is a reason for that, isn't it?

Discussions about Android 5.x - 6.x are off-topic here.

Remember that VMOS and F1VM environments are NOT SUPPORTED!

These "virtual" environments are not supported by Termux. They have a number of issues including broken apt-key.

Discussions about VMOS and F1VM are off-topic here.