This is the message I got from the tech at the hosting company.

Hello Maurice,

Thank you for your patience so far.

I have further reviewed the matter on my end and following the provided step-by-step instructions via the Upgrading guide:

http://learn.elgg.org/en/stable/admin/upgrading.html#from-2-3-to-3-0

I have changed the current PHP version to PHP 7.1 and also increased the PHP values to the maximum values.

After that I have changed the PHP version in the composer.json file from PHP 5.6 to PHP 7.1:

https://www.screencast.com/t/fILoDaOSM

and in the .htaccess replaced

RewriteRule ^(.*)$ index.php?__elgg_uri=$1 [QSA,L]

with

RewriteRule ^(.*)$ index.php [QSA,L]

The next step as described are the following composer commands:

composer self-update

cd ./path/to/project/root
composer require elgg/elgg:~3.0.0
composer update
vendor/bin/elgg-cli upgrade async -v

so I have upgraded composer 1.9 to composer 1.10

https://www.screencast.com/t/5NuijDyV

and composer2 from version 2.0.8 to version 2.1.8:

https://www.screencast.com/t/HnafdikB

Once I have executed the next command:

composer require elgg/elgg:~3.0.0

by using composer2 the following error occurred:

Problem 1
- elgg/elgg[3.0.0-beta.1, ..., 3.0.x-dev] require elgg/login_as ~2.0.0 -> found elgg/login_as[2.0.0] but the package is fixed to 1.9.2 (lock file version) by a partial update and that version does not match. Make sure you list it as an argument for the update command.
- Root composer.json requires elgg/elgg ~3.0.0 -> satisfiable by elgg/elgg[3.0.0-beta.1, ..., 3.0.x-dev].

Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.

So with this in mind I have used the suggested command with --with-all-dependencies:

composer2 require elgg/elgg:~3.0.0 --with-all-dependencies

and another error occurred:

Problem 1
- elgg/elgg[3.0.0-beta.1, ..., 3.0.x-dev] require bower-asset/jquery ^2.1.4 -> found bower-asset/jquery[2.2.4] in the lock file but not in remote repositories, make sure you avoid updating this package to keep the one from the lock file.
- elgg/elgg[3.0.0-rc.2, ..., 3.0.7] require bower-asset/fontawesome ~5.6 -> could not be found in any version, there may be a typo in the package name.
- Root composer.json requires elgg/elgg ~3.0.0 -> satisfiable by elgg/elgg[3.0.0-beta.1, ..., 3.0.x-dev].

Potential causes:
- A typo in the package name
- The package is not available in a stable-enough version according to your minimum-stability setting
see <https://getcomposer.org/doc/04-schema.md#minimum-stability> for more details.
- It's a private package and you forgot to add a custom repository to find it

I have also attempted to update the feature by using composer version 1.10, however without success because other errors have been detected:

Problem 1
- elgg/elgg 3.0.x-dev requires bower-asset/sprintf ~1.0.3 -> no matching package found.
- elgg/elgg 3.0.7 requires bower-asset/fontawesome ~5.6 -> no matching package found.
- elgg/elgg 3.0.6 requires bower-asset/fontawesome ~5.6 -> no matching package found.
- elgg/elgg 3.0.5 requires bower-asset/fontawesome ~5.6 -> no matching package found.
- elgg/elgg 3.0.4 requires bower-asset/fontawesome ~5.6 -> no matching package found.
- elgg/elgg 3.0.3 requires bower-asset/fontawesome ~5.6 -> no matching package found.
- elgg/elgg 3.0.2 requires bower-asset/fontawesome ~5.6 -> no matching package found.
- elgg/elgg 3.0.1 requires bower-asset/fontawesome ~5.6 -> no matching package found.
- elgg/elgg 3.0.0-rc.2 requires bower-asset/fontawesome ~5.6 -> no matching package found.
- elgg/elgg 3.0.0-rc.1 requires bower-asset/sprintf ~1.0.3 -> no matching package found.
- elgg/elgg 3.0.0-beta.3 requires bower-asset/sprintf ~1.0.3 -> no matching package found.
- elgg/elgg 3.0.0-beta.2 requires bower-asset/sprintf ~1.0.3 -> no matching package found.
- elgg/elgg 3.0.0-beta.1 requires bower-asset/sprintf ~1.0.3 -> no matching package found.
- elgg/elgg 3.0.0 requires bower-asset/fontawesome ~5.6 -> no matching package found.
- Installation request for elgg/elgg ~3.0.0 -> satisfiable by elgg/elgg[3.0.0, 3.0.0-beta.1, 3.0.0-beta.2, 3.0.0-beta.3, 3.0.0-rc.1, 3.0.0-rc.2, 3.0.1, 3.0.2, 3.0.3, 3.0.4, 3.0.5, 3.0.6, 3.0.7, 3.0.x-dev].
 

Potential causes:
- A typo in the package name
- The package is not available in a stable-enough version according to your minimum-stability setting
see <https://getcomposer.org/doc/04-schema.md#minimum-stability> for more details.
- It's a private package and you forgot to add a custom repository to find it

Having all this in mind it appears the upgrading process is out of our scope of experience and it requires developer knowledge. This is why I would advise you to contact a Certified Web Developer in order to review the issues and find the best resolution.