sfdx force:org:create -s -f config/project-scratch-def.json -a "UploadFileFlowMobile"
sfdx force:source:push
sfdx force:source:convert -d mdapioutput/
sfdx force:mdapi:deploy -d ./mdapioutput -u YourOrgAlias -w 100
https://developer.salesforce.com/docs/atlas.en-us.salesforce_vpm_guide.meta/salesforce_vpm_guide/vpm_files.htm https://releasenotes.docs.salesforce.com/en-us/spring18/release-notes/rn_forcecom_flow_file.htm https://salesforcesidekick.com/2018/01/15/the-lowdown-on-uploading-a-file-inside-a-flow/
Process Automation Settings > Enable Lightning runtime for flows
Add existing action to pagelayouts or create new action on other objects, referencing the FlowUploadFile flow. The recordId variable is automatically linked with the Record Id When added as an action, the button will be visible on the Salesforce app also.
The flow can also be added to a lightning page (this will not be visible for mobile devices).