How to move Magento 2.1.9 from bitnami to a similar bitnami box Azure but at Magento version 2.3.3
Also, If I upgrade Magento via composer or using the admin panel then will all of the third-party extensions work fine?
Please check the official doc from Magento.
https://devdocs.magento.com/guides/v2.3/comp-mgr/cli/cli-upgrade.html
If all third party extension supports PHP version and newly upgraded Magento code than it will. In 95% cases, it supports, in cases so old extension version does not because they some times not support PHP version or code changes in core or whatever reason. We personally have an issue after upgrading which solved within an hour.
There are tree way to upgrade magento2.
Best way is using composer. Open you composer.json file from magento root directory. Replace 2.1.9 to 2.3.3 in "version" and ""magento/product-community-edition" value.
After Remove var/cache, pub/static/frontend , pub/static/adminhtml, generated folder.
rm -rf var pub/static/frontend pub/static/adminhtml generated
Run command.
bin/magento setup:upgrade;
bin/magento setup:di:compile;
bin/magento indexer:reindex;
bin/magento setup:static-content:deploy -f
After successfully execute above command set permission 777 to your var and pub folder.
sudo chmod -R 777 var pub generated;
check your magento version.
bin/magento --version
Magento2 has direct upgrade from admin panel. See below link
https://devdocs.magento.com/guides/v2.3/comp-mgr/upgrader/ce-ee-upgrade-start.html
Upgrade this way if the previous two method be failed.
Download the latest Magento 2 version from "https://magento.com/tech-resources/download".
Unzip it in your magento root folder. that will override your vendor and core magento files.
Then run:
php bin/magento setup:upgrade;php bin/magento setup:di:compile;php bin/magento indexer:reindex;php bin/magento setup:static-content:deploy -f
And update your magento var pub and generated folder permission and check your magento version.