Office 365
Branding
Site Designs and Site Scripts (2018.5)
https://laurakokkarinen.com/the-ultimate-guide-to-sharepoint-site-designs-and-site-scripts/
Themes (2019.2)
https://laurakokkarinen.com/how-to-create-a-multicolored-theme-for-a-modern-sharepoint-online-site/
Theming Web Part (2019.3)
https://n8d.at/blog/panthema-web-part-is-now-release-know-your-sharepoint-theme-colours/
Branding SharePoint: The New Normal
https://bob1german.com/2018/09/04/branding-sharepoint-the-new-normal/
Repost
https://techcommunity.microsoft.com/t5/Microsoft-SharePoint-Blog/Branding-SharePoint-The-New-Normal/ba-p/241855
Theme Generator
https://developer.microsoft.com/en-us/fabric#/styles/themegenerator
Classic vs Modern
Is It Time to Give Up SharePoint Classic Sites?
http://www.markrackley.net/2018/01/30/is-it-time-to-give-up-sharepoint-classic-sites/
How and When to Adopt the Modern UI in SharePoint – 2 Part Series
https://nathanwellsblog.com/2017/07/23/how-and-when-to-adopt-the-modern-ui-in-sharepoint-part-12/
https://nathanwellsblog.com/2017/09/01/how-and-when-to-adopt-the-modern-ui-in-sharepoint-part-22/
List and Site Templates
Save list as template on modern team site not available in SharePoint Online
https://sharepoint-specialist.nu/save-list-as-template-on-modern-team-site-not-available-in-sharepoint-online-e85c25a12943
Save Modern Team Site as a template & provision using Classic Team Site method (visible in SP Admin)
https://techcommunity.microsoft.com/t5/SharePoint/Save-Modern-Team-Site-as-a-template-amp-provision-using-Classic/td-p/95307
Create and use site templates
https://support.office.com/en-us/article/create-and-use-site-templates-60371b0f-00e0-4c49-a844-34759ebdd989
“Just to be clear. Using save-site-as-a-template with modern team sites or publishing sites is NOT supported. You can always find ways with tenant admin permissions to achieve things, but the fact that it's doable does not mean it's supported.
Any sites created with the template which has been produced with this method can have unexpected issues in the future, so provided steps should never be used.”
Best regards,
Vesa Juvonen, Senior Program Manager, SharePoint Engineering, Microsoft.