App script onedit function - non-google users

I have the following code:

function onEdit(e) {
  const sheetRegex = /^(Sheet1)$/i;
  const emailColumn = 1; 
  let sheet;
  if (!e
    || !e.range
    || e.range.columnStart <= emailColumn
    || !(sheet = e.range.getSheet()).getName().match(sheetRegex)) {
    return;
  }
  const emailCell = sheet.getRange(e.range.rowStart, emailColumn);
  if (!emailCell.getDisplayValue()) {
    SpreadsheetApp.getUi().alert("Please enter a valid email address");
    emailCell.activate();
  }
}

I am trying to insure that users enter an email address when filling in the spreadsheet. It works perfectly fine when the user is logged in to a google account. If the user uses another browser other than chrome or uses incognito mode, it does not work. Is there anyway around this?

So unfortunately if you explicitly want to access the ui (via SpreadsheetApp.getUi()), you will not be able to get this to work for non-logged in users.

I presume that you are using a simple trigger (ie just using the reserved onEdit method name). Per the comments in this question and Google's documentation, simple triggers do not request authorization explicitly from the end user, but they do run under the authorization of the end user, meaning that they need to be logged in properly.

You can use Installable Triggers, which allows the function to run under your authorization every time. You can find instructions on how to set that up according to these instructions (but essentially, you just rename the function to something other than onEdit and enable it under the Triggers tab on the left-hand side of the Apps Script Editor). Unfortunately (or fortunately for security reasons), these triggers will not run for not logged in users if you are accessing sensitive/restricted resources, which seems to include the UI elements (as was discussed here).

I confirmed that the simplest script (that just edits another cell) run as an installable trigger does work for logged in users, not logged in users, and in incognito mode, but the SpreadsheetApp.getUi() only works for logged in users.

Depending on your use case, you may be able to modify your script so that it (a) runs as an installed trigger and (b) only performs simple operations to alert the user. I unfortunately cannot be more specific on that last part, as I can't find any documentation from Google on this, so you may have to play around with it, but maybe just something like putting big bold letters in an adjacent cell to warn the user would be sufficient.